Aggregate Base Course often referred simply as ABC, has certain desirable properties. Base Course in pavements refers to the sub-layer material of an asphalt roadway and is placed directly on top of the undisturbed soil so as to provide a foundation to support the top layer(s) of the pavement. It is typically made of a recipe of different sizes and quality of aggregate rock inclusive of 3/4 in (19.05 mm) to fine dust. An aggregate is normally made from newly quarried rock, or it is sometimes allowed to be made from recycled asphalt, or Portland cement concrete.
Aggregate Base is used as the base course under asphalt pavement roadways, under Portland cement concrete slabs and structural foundations, and as backfill material for underground pipelines and other underground utilities within a roadway. It is placed by means of attentive spreading and compacting to a minimum of 95% relative compaction, thus providing the stable foundation needed to support a pathway,foundation,driveway or roadway.
The Sub-Base is the layer of fined chipped aggregate material, typically Crusher Fines,which is laid above the ABC. The thickness of sub-base can range from 3/4″ – to 1″ for garden paths and 2″ inches for driveways and public footpaths, depending on anticipated traffic.